The British pound plunged 10 percent, the most since 1985, the euro fell the furthest since its introduction in 1999, while the Japanese yen had its biggest surge since 1998. Oil fell to $47 per barrel. Gold soared along with US Treasuries as panicked investors sought a safe haven from the markets.

“Investors are just trying to get out. You sell first and ask questions later. There was a massive miscalculation of risk and now you're seeing all that unwind,” head of investment strategy at Perpetual Ltd. in Sydney, Matthew Sherwood, told Bloomberg.

The outcome of the Brexit referendum has caused reaction at home and worldwide. Sinn Fein has said: "The British [have] forfeited any mandate to represent [the] economic or political interests of people in Northern Ireland."

The leader of the French National Front Marine Le Pen hailed the success and called for a similar EU referendum in France.

“Like a lot of French people, I’m very happy that the British people held on and made the right choice. What we thought was impossible yesterday has now become possible,” she said as cited by the Guardian.

Dutch right-wing politician Geert Wilder also wants the Netherlands to decide on whether to stay in the EU.

Britain’s Prime Minister David Cameron, a fierce proponent of staying in the EU, has announced he will step down by October.

“The British people have made a very clear decision to take a different path and as such, I think the country requires fresh leadership to take it in this direction," Cameron told reporters.

“I will do everything I can as prime minister to steady the ship over the coming weeks and months, but I do not think it would be right for me to try to be the captain that steers our country to its next destination,” the British PM said, stressing that the country needs stability and new leadership.

“There is no need to have a precise timetable today, but in my view we should aim to have a new prime minister in place by the start of the Conservative Party congress in October," Cameron said.

German Foreign Minister Frank-Walter Steinmeier has been among the first in Europe to react, calling the Brexit result “truly sobering and sad.”

“We respect the result. We have clarity for the UK to go its own way,” president of the European Parliament, Martin Schulz, said

“Now is the time for us to behave seriously and responsibly. David Cameron has his responsibilities for his country, we have our responsibilities for the future of the EU. You can see what is happening to sterling on the markets. I don't want the same thing to happen to the euro,” Schulz said.

“Damn! A bad day for Europe,” German Vice-Chancellor Sigmar Gabriel tweeted.